docs: def _get_stddevs(self, C, stddev_types, num_sites):
          """
          Return total standard deviation.
          """
          assert all(stddev_type in self.DEFINED_FOR_STANDARD_DEVIATION_TYPES
                     for stddev_type in stddev_types)
  
          # Using a frequency independent value of sigma as recommended
          # in the caption of Table 2 of Atkinson (2010)
          stddevs = [0.26/np.log10(np.e) + np.zeros(num_sites)]
  
          return stddevs